The prior art includes many patents disclosing retractable tag axle assemblies for concrete mixing trucks. When the tag axle assemblies are in their lowered road engaging position, the truck is able to carry larger weights yet still meet federal road restrictions. The tag axle assemblies are made retractable so that they do not interfere with off-road travel at the job site or with the discharge of concrete from the truck.
A real problem with many prior art designs is that, as the tag axle assembly is raised or lowered, it will bind with the truck's collector chute or distribution chute. To avoid this problem, some prior art designs have required the chutes to be removed or partially removed from the truck during extension or retraction of the tag axle assembly. In other designs (such as those described in U.S. Pat. No. 3,112,100 to E. S. Prichard and U.S. Pat. No. 3,877,715 to Thayer, et al), the chutes are secured to the tag axle assembly itself rather than directly to the drum supporting pedestal of the concrete mixing truck. These designs suffer from the inability to maintain the close tolerances necessary to avoid unnecessary waste and spillage of concrete.
A rather unique chute arrangement is disclosed in expired U.S. Pat. No. 3,317,193 to Buelow, et al. This patent discloses a concrete mixing truck having a tag axle assembly. The truck also includes a pivoting discharge chute mounted to and supported by a pedestal, via a linkage assembly. While the discharge chutes are supported by the truck pedestal rather than by the tag axle assembly, the Buelow design suffers from several problems. For example, the pivot for the tag axle assembly is more forward and higher than is necessary. As such, the design does not provide full advantage with respect to weight restrictions. More importantly, Buelow includes no reliable means for ensuring that the tag axle assembly will not interfere with, damage or be damaged by the concrete discharge chute as the tag axle assembly is raised or lowered.
Thus, there is a real need for a tag axle assembly/cement truck design: (1) which takes full advantage with respect to weight restrictions so that increased payloads can be hauled over the highways without violating government imposed road restrictions; (2) in which the discharge chute(s) are securely attached to the drum pedestal within close tolerances to the discharge opening to avoid unnecessary spillage of concrete; and (3) which includes the provision of reliable means for precluding the raising or lowering of the tag axle assembly unless the chutes are in a position in which they will not contact the tag axle assembly.